Group B Streptococcus (GBS) is a major cause of neonatal sepsis and meningitis. First emerging as a pathogen in newborn nurseries in the 1970s, it is now a pathogen of concern in nursing homes, intensive care units and outpatient settings. Little is known about GBS virulence factors. The overall goals of this application are 1) to use genetic fingerprinting techniques to better describe the molecular epidemiology of GBS of several epidemiologically defined collections; and 2) to identify new genes associated with GBS disease. By combining epidemiologic information with molecular genetics, we can maximize our ability to detect GBS virulence-related genes associated with invasive disease, extra-intestinal colonization, transmission and antibiotic resistance. This strategy also gives us insight as to the relative importance of the identified genes and their potential mechanism. A better understanding of the molecular epidemiology and the identification of new GBS virulence genes will facilitate the discovery of new therapies and prevention strategies for GBS disease.